Silicon iron castings and method of making the same



Patented June 7, 1932 UNITED STATES FRANK S. HODSON, OF PHILADELPHIA,PENNSYLVANIA SILICON IRON CASTINGS AND METHOD OF MAKING THE SAME RDrawing.

The principal object of the present invention is to provide silicon ironcastings which can be machined and which are possessed of the desirablenon-corrosive properties of known high silicon iron castings.

To these and other ends hereinafter set forth theinvention,-generallystated, comprises machinable high silicon ironcastings.

The invention also comprises the method of producing such machinablehigh silicon iron castings which consists in adding antimony to themolten silicon iron prior to casting.

The invention also comprises the improvements to be presently describedand finally claimed.

For the sake of further description it may be said that an ordinary.high silicon iron casting, which is not machinable, may respond to, forexample, the following analysis m of components other than iron:

Silicon 8.00 to 20.00 Manganese .25 to 2 Sulphur; 0.01 to 0.15 2.3.Phosphorus 0.05 to 0.20

Total carbon 0.20 to 3.50

The analysis referred to is merely descriptive and varies considerablywith known high silicon content iron castings which, however,

as has been said, are not machinable. Con trasted with suchnon-machinable silicon iron castings machinable-silicon iron castings ofthe present invention may, for convenience, and not by way of limitationreferring to the same analysis, be described as responding to thefollowing constituents other than iron:

Silicon 8.00 .to 20.00 Manganese .25 to 2.50 Q Sulphur Traces to .15Phosphorus Traces to .20

Total carbon 0.20 to 3.50

0 in tranve'rse strength.

Application filed May 10, 1929. Serial No. 362,123.

To practice the invention metallic antimony is added to the molten highsilicon iron prior to casting. The antimony produces a finer crystallineform in the final alloy. The antimony tends to break up silicon andreduces the nlfmber of silicates found in the finished alloy. A certainamount of the antimony is dissipated but some remains in the finalalloy. The temperature ofthesilicon iron prior to casting is higher thanthemelting point and the boiling point of antimony, so that although amajor portion of the antimony is dissipated some must appear in thefinal casting. However, the antimony imparts to the castingmachinability while permitting the finished casting to retain thequality of being highly resistant to a great number of corrosivesubstances.

As an example of proportions and in respect to antimony mention may bemade to 0003125 to .1 of the total alloy or high silicon 1ron.

By Way of further description it may be said in respect to high siliconiron metals or alloys such as are now employed for making high siliconiron castings which are not machinable, the quality of machinability isadded by the addition of antimony, as has been described, and theproportion in which the antimony is used is dependent upon the degree ofmachinability desired, but as a practical matter the range given is agood guide and falls within safe limits.

I claim:

1. The process of making machinable high silicon iron castings whichconsists in adding sufiicient antimony to the molten metal before it iscast to leave antimony weighing from 0.0003 to 0.1 of the total Weightof the alloy in the casting.

2. A machinable, high silicon iron casting containing silicon 8.0 to20.0%, manganese 0.25 to 2.50%, sulphur traces to 0.15%, phosphorustraces to 0.20%, total carbon 0.20 to 3.50%, and antimony 0.0003125 to0.1%.

3. A machinable, high silicon iron casting containing silicon 8.0 to20.0% and antimony 0.0003125 to 0.1%.

FRANK S. HODSON.

